Hemming apparatus

ABSTRACT

A lower platen is provided with a hem punch and a slide cam. The hem punch is floating-supported to the slide cam. An upper platen is provided with a hem punch driver cam and a liner. The hem punch driver cam is used to change the hem punch to a pre-hemming position and to a final hemming position. The liner applies a processing load to the hem punch being in the final hemming position. By moving the hem punch to which the processing load is applied from the liner, a final hemming part of the hem punch is pressed against a bent portion of the workpiece.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 to Japanese Patent Application No. 2007-166544 filed on Jun. 25, 2007, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

This invention relates to hemming apparatuses for hemming workpieces, such as metal plates.

(b) Description of the Related Art

Hemming apparatuses are conventionally known for hemming workpieces, such as door panels for motor vehicles. An example of such a hemming apparatus is disclosed in Japanese Patent Publication No. 3598489. The hemming apparatus includes upper and lower platens arranged opposite to each other and is configured to vertically move the upper platen by means of a driving mechanism.

The lower platen is provided with a hemming die for supporting a workpiece from below and a cushion holder separate from the hemming die. The hemming die is fixed to the lower platen against vertically moving relative to the lower platen. The cushion holder is supported from below by a vertically extendable gas spring and thereby can be vertically moved. A slide cam is attached through a guide mechanism to the top surface of the cushion holder to allow its movement in a direction towards and away from the workpiece. A hem punch for processing a bent portion of the workpiece is fixed to the slide cam. The hem punch includes a pre-hemming part for preliminarily hemming the bent portion of the workpiece and a final hemming part for finally hemming the preliminarily hemmed portion of the workpiece to a final shape.

On the other hand, the upper platen includes a driver cam capable of engaging the slide cam to move the slide cam and a liner for applying a processing load to the hem punch.

In hemming the bent portion of the workpiece with the hemming apparatus, the workpiece is first put on the hemming die of the lower platen. The bent portion of the workpiece is previously formed to rise from the workpiece body. Then, the upper platen is moved down. When the upper platen moves down, the driver cam of the upper platen pushes the slide cam of the lower platen. Thus, the slide cam and hem punch of the lower platen are guided by the guide mechanism to move on the cushion holder towards the bent portion of the workpiece, so that the pre-hemming part of the hem punch is pressed against the bent portion of the workpiece from laterally to apply a hemming force to the bent portion. The bent portion of the workpiece having received the hemming force from laterally is folded into a preliminarily hemmed state. After the above pre-hemming step, the hem punch is further moved by the driver cam until its final hemming part reaches a position facing the bent portion of the workpiece. At this timing, the liner of the upper platen pushes down the hem punch to apply a processing load to the hem punch. The processing load applied to the hem punch acts through the slide cam and the guide mechanism on the cushion holder, whereby the cushion holder moves down against an urging force of the gas spring. Thus, the hem punch moves down and the final hemming part of the hem punch is pressed against the bent portion of the workpiece. As a result, the bent portion is formed into a final shape.

Therefore, the hemming apparatus can perform both preliminary hemming and final hemming of the bent portion of the workpiece while holding the workpiece with the same member, thereby reducing the number of process steps.

In the above hemming apparatus, the lower platen is provided with the cushion holder and the gas spring and configured to move down the cushion holder with a processing load applied from the liner of the upper platen. Thus, in finally hemming the bent portion of the workpiece, the hem punch can be moved down to press the final hemming part against the bent portion of the workpiece. However, the cushion holder is so large that the slide cam and the guide mechanism can be attached to it and, therefore, the gas spring for supporting the cushion holder must be strong and large.

Since the cushion holder and the gas spring are large, the above hemming apparatus has a large size and poor maintainability. Furthermore, in view of the workpiece shape and the structure of the hemming apparatus, the portion of the cushion holder receiving the processing load from the liner must be away from the portion thereof supported to the gas spring. Therefore, it can be believed that misalignment occurs between the portion of the cushion holder receiving the processing load and the portion thereof supported to the gas spring to prevent the processing force from being applied to the cushion holder in a well-balanced manner and place a strain on the cushion holder, thereby shortening the lifetime of the hemming apparatus.

The present invention has been made in view of the foregoing points and, therefore, an object thereof is to move the hem punch during final hemming of the bent portion of the workpiece without providing any cushion holder and any gas spring for supporting the cushion holder and allow the hem punch to finally hem the bent portion, thereby downsizing the hemming apparatus and enhancing its maintainability, and to prevent a strain from being applied to the hemming apparatus, thereby extending its lifetime.

SUMMARY OF THE INVENTION

A first aspect of the invention is directed to a hemming apparatus for hemming a bent portion of a workpiece previously formed to rise from the body of the workpiece. The hemming apparatus includes: a first platen including a hemming die for supporting the workpiece, a hem punch including a pre-hemming part and a final hemming part both for hemming the bent portion of the workpiece, a slide cam to which the hem punch is attached, a slide cam guide mechanism for guiding the slide cam in a direction to laterally move the slide cam towards and away from the bent portion, and a hem punch support mechanism for floating-supporting the hem punch to the slide cam; and a second platen disposed to face the first platen and including a hem punch driver cam engageable with the slide cam and a load application mechanism for applying a processing load to the hem punch. Furthermore, the hem punch driver cam is configured to move the slide cam to change the hem punch to a pre-hemming position at which the pre-hemming part is pressed against the bent portion of the workpiece and to a final hemming position at which the final hemming part faces the bent portion of the workpiece. Furthermore, the load application mechanism is configured to apply a processing load to the hem punch being in the final hemming position.

According to the above configuration, when, for example, the second platen is moved towards the first platen, the slide cam of the first platen engaging the hem punch driver cam of the second platen moves, so that the hem punch reaches a pre-hemming position and the pre-hemming part is pressed against the bent portion of the workpiece supported to the hemming die. Thus, the bent portion of the workpiece is preliminarily hemmed. Then, when the slide cam is further moved by the hem punch driver cam to bring the hem punch to a final hemming position, the final hemming part reaches a position facing the bent portion of the workpiece. A processing load is applied to the hem punch in the final hemming position by the load application mechanism. At this time, since the hem punch is floating-supported to the slide cam, the hem punch can be moved in a direction to process the workpiece without providing any cushion holder and any gas spring supporting the cushion holder as in the known art, whereby the final hemming part of the hem punch can be pressed against the bent portion of the workpiece. Thus, the bent portion of the workpiece is finally hemmed into a final shape.

Since, as described above, the cushion holder and the gas spring can be dispensed with, this downsizes the hemming apparatus and enhances its maintainability. In addition, since a processing load is applied to the hem punch for processing the bent portion of the workpiece, no strain is placed on the hemming apparatus, which elongates the lifetime of the hemming apparatus.

The above effects apply also to the case where the first platen is moved towards the second platen.

The hem punch support mechanism preferably includes a hem punch urging member urging the hem punch opposite to a direction in which the processing load is applied.

According to the above configuration, the hem punch can be floating-supported to the slide cam by simply releasing the hem punch from the processing load. Therefore, the hem punch can be floating-supported with a simple structure, thereby reducing the cost.

The hemming apparatus may further include a workpiece holder for holding a held portion formed in the workpiece by pressing the workpiece holder against the held portion. Preferably, the workpiece holder includes a pad bearable against the held portion of the workpiece, a pad support mechanism for supporting the pad to the second platen and moving the pad in a direction towards and away from the held portion of the workpiece, and a pad driver cam disposed on the first platen and engageable with the pad support mechanism, and the pad driver cam is configured to actuate the pad support mechanism to switch the pad between a position close to the held portion of the workpiece and a position away from the held portion.

According to the above configuration, when the second platen is moved towards the first platen, the pad support mechanism of the second platen engaging the pad driver cam of the first platen is actuated, so that the pad moves to a position close to the held portion of the workpiece and is pressed against the held portion. This makes it difficult for the bent portion of the workpiece to be displaced during hemming, thereby increasing the processing precision. The same applies to the case where the first platen is moved towards the second platen.

The pad support mechanism preferably includes a link connecting the pad to the second platen, and a pad urging member urging the pad in a direction away from the held portion of the workpiece.

According to the above configuration, the pad position can be changed with a simple structure using the link and the pad urging member, thereby reducing the cost.

The hem punch may comprise a plurality of spaced-apart hem punches, and the pad of the workpiece holder may be disposed between each two adjacent said hem punches.

According to the above configuration, the bent portions located on both sides of each held portion held by the pad are hemmed. Since the portion of the workpiece between each adjacent bent portions is held by the pad, this prevents displacement of the bent portions located on both sides of it. Thus, the processing precision of the bent portions of the workpiece can be further increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a lower platen of a hemming apparatus according to an embodiment of the present invention.

FIG. 2 shows an upper platen of the hemming apparatus as viewed from below.

FIG. 3A is a plan view of the hemming apparatus when outer peripheral corner pre-hemming mechanisms are actuated, and FIG. 3B is a plan view of the hemming apparatus when an upper end hemming mechanism, inner periphery hemming mechanisms and outer periphery hemming mechanisms are actuated.

FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 1 when the upper platen moves up.

FIG. 5 is a cross-sectional view taken along the line V-V of FIG. 1 when the upper platen moves up.

FIG. 6 is a corresponding view of FIG. 5 when a bent portion of a workpiece is preliminarily hemmed.

FIG. 7 is a corresponding view of FIG. 5 when the bent portion of the workpiece is finally hemmed.

FIG. 8 is an enlarged view showing the bent portion of the workpiece and its surrounding in FIG. 7.

FIG. 9 is a cross-sectional view taken along the line VII-VII of FIG. 1.

FIG. 10 is an enlarged view showing the bent portion of the workpiece and its surrounding in FIG. 9.

FIG. 11A is an enlarged view of a hem punch and a pad just before preliminary hemming, and FIG. 11B is an enlarged view of the hem punch and the pad just after final hemming.

DETAILED DESCRIPTION OF THE INVENTION

A detailed description is given below of an embodiment of the present invention with reference to the drawings. The following description of the preferred embodiment is merely illustrative in nature and is not intended to limit the scope, applications and use of the invention.

As shown in FIGS. 1 and 2, a hemming apparatus 1 according to an embodiment of the invention includes upper and lower platens 2 and 3 disposed to vertically face each other, and a driving mechanism (not shown) for vertically moving the upper platen 2 towards and away from the lower platen 3. The driving mechanism is constituted, such as by a well-known hydraulic cylinder.

Workpieces W to be processed by the hemming apparatus 1 are doors to be disposed at the sides of motor vehicles. An upper part of the door body includes a sash. The door body includes, as partly shown in FIG. 4, a body inner panel W1, a body outer panel W2 and an outer reinforcing member W4. An upper end part of the body inner panel W1 (the left end thereof in FIG. 4) and an upper end part of the body outer panel W2 are kept away from each other in the width direction of the vehicle body (the vertical direction in FIG. 4). A window glass (not shown) moves up and down in a space between the upper end parts of both the panels W1 and W2. The outer reinforcing member W4 is composed of a plate material and disposed on an upper part of the inner surface of the body outer panel W2 (the surface thereof towards the body inner panel W1). An upper end part of the outer reinforcing member W4 is configured to be clamped under the hemmed upper end part of the body outer panel W2, while a lower end part thereof is adhered to the inner surface of the body outer panel W2, such as with adhesive. The upper end part of the body outer panel W2 has two bent portions Wa and Wa (shown in FIGS. 11A and 11B) for clamping the outer reinforcing member W4 thereunder. The two bent portions Wa and Wa are disposed a distance away from each other in the longitudinal direction of the upper end part. The bent portions Wa and Wa are portions to be folded down (hemmed) by the hemming apparatus 1. The portion of the upper end part of the body outer panel W2 located between the bent portions Wa and Wa, although described later in detail, is a held portion Wb against which a pad 60 of the hemming apparatus 1 is to be pressed.

Although not shown, the door sash is formed of a combination of a sash inner panel with a sash outer panel. A channel member for holding the peripheral part of the window glass is disposed between the sash inner and outer panels. The sash outer panel includes inner periphery bent portions formed at the inner periphery thereof and outer periphery bent portions formed at the outer periphery thereof. The inner periphery bent portions are configured to lie over an end part of the channel member when they are hemmed. The outer periphery bent portions are likewise configured to lie over the outer periphery of the sash inner panel when they are hemmed.

As shown in FIG. 1, on the top surface of the lower platen 3, an upper end hemming mechanism A is fixedly disposed to correspond to the shape of the upper edge of the body outer panel W2. As also shown in FIGS. 3A and 3B, on the top surface of the lower platen 3, inner periphery hemming mechanisms B, C and D are also fixedly disposed to correspond to the shape of the inner periphery of the sash.

A hemming die 10 for supporting the workpiece W from below is disposed on the lower platen 3 to face the upper end hemming mechanism A and the inner periphery hemming mechanisms B, C and D. Around the outer periphery of the hemming die 10, outer periphery pre-hemming mechanisms a, c and e and outer peripheral corner pre-hemming mechanisms b and d are arranged to correspond to the shape of the outer periphery of the sash of the workpiece W. The lower platen 3 constitutes a first platen of the hemming apparatus according to the present invention.

The upper end hemming mechanism A and the inner periphery hemming mechanisms B, C and D have the same structure. Therefore, a detailed description is given below only of the structure of the upper end hemming mechanism A. As shown in FIG. 4, the upper end hemming mechanism A includes a slide cam 30, a slide cam urging mechanism 31 supporting the slide cam 30 to the top surface of the lower platen 3 while urging it in a predetermined direction, two hem punches 32 and 32 (see FIGS. 1, 11A and 11B) attached to an upper part of the slide cam 30, and a hem punch support mechanism 33 floating-supporting the hem punches 32 (i.e., supporting them in their floating positions). The hem punches 32 and 32 are spaced apart from each other in a direction of extension of the bent portions Wa and Wa of the workpiece W. The distance between the hem punches 32 and 32 is set so that the held portion Wb is exposed from between the hem punches 32 and 32.

As shown in FIG. 4, the slide cam urging mechanism 31 includes a lower platen-fixed member 31 a fixed to the top surface of the lower platen 3. The slide cam 30 is engaged with the lower platen-fixed member 31 a to inhibit vertical movement of the slide cam 30 relative to the lower platen 3. The lower platen-fixed member 31 a extends along the top surface of the lower platen 3 in a direction towards and away from the hemming die 10. Therefore, the slide cam 30 is horizontally guided to move towards and away from the hemming die 10. The slide cam urging mechanism 31 further includes a spring 31 b as an urging member urging the slide cam 30 in a direction away from the hemming die 10 (the direction shown in the arrow Y in FIG. 4).

The top of the slide cam 30 has an indentation 30 a formed in a part thereof close to the hemming die 10 to cut away the slide cam 30. The hem punches 32 are disposed in the indentation 30 a. The bottom wall of the indentation 30 a extends substantially horizontally, while the side wall thereof extends substantially vertically. A plate 33 a constituting part of the hem punch support mechanism 33 is fixedly attached to the side wall of the indentation 30 a to extend vertically. The slide cam 30 is provided with two guide pins 36 projecting upward from the bottom wall of the indentation 30 a. Furthermore, as shown in FIG. 5, the slide cam 30 has two holes 30 b formed in the bottom wall of the indentation 30 a. Each hole 30 b receives a lower part of a spring 33 b serving as a hem punch urging member constituting part of the hem punch support mechanism 33. The spring 33 b supports the associated hem punch 32 from below and urges it upward. The other part of the spring 33 b extends upward beyond the bottom wall of the indentation 30 a.

The slide cam 30 has a cam face 30 c on the opposite side to the indentation 30 a. The cam face 30 c is composed of an inclined plane inclined to gradually come close to the indentation 30 a as it goes upward.

A portion of each hem punch 32 facing the plate 33 a extends vertically along the plate 33 a. Furthermore, as shown in FIG. 4, each hem punch 32 includes a cylindrical bush 37 disposed at a portion thereof corresponding to the associated guide pin 36 to extend vertically. The bush 37 is configured to slide the guide pin 36 therein. Therefore, the hem punches 32 moves only vertically relative to the slide cam 30. Furthermore, as shown in FIG. 5, each hem punch 32 has a hole 32 a formed in the bottom surface thereof coaxially with the associated hole 30 b in the slide cam 30. The hole 32 a receives an upper part of the associated spring 33 b. Each spring 33 b is mounted on a bolt 35 vertically passing through the associated hem punch 32 and fastened to the slide cam 30. In this state, each hem punch 32 assumes a floating position upward away from the bottom wall of the indentation 30 a of the slide cam 30. In other words, the hem punches 32 are floating-supported to the slide cam 30 so that they can move only in a direction of movement of the upper platen 2.

Each hem punch 32 has also a forming part 32 b formed to extend beyond the slide cam 30 towards the hemming die 10. The forming part 32 b includes a pre-hemming part 32 c for preliminarily hemming the associated bent portion Wa of the workpiece W and a final hemming part 32 d for hemming the preliminarily hemmed portion of the workpiece W to a final shape. The final hemming part 32 d is disposed in the side of the bottom surface of the forming part 32 b located towards the root end thereof (towards the slide cam 30) and composed of a substantially horizontally extending plane. The pre-hemming part 32 c is disposed in the side of the bottom surface of the forming part 32 b located towards the distal end thereof (towards the hemming die 10) and composed of a plane inclined to become higher with going away from the slide cam 30. The angle of inclination of the pre-hemming part 32 c determines the preliminarily hemmed shape of the associated bent portion Wa.

Each of the inner periphery hemming mechanisms B to D includes a hem punch 42 and a slide cam 43 both of which have the same structures as those of the upper end hemming mechanism A.

Referring back to FIG. 1, each of the outer periphery pre-hemming mechanisms a, c and e and the outer peripheral corner pre-hemming mechanisms b and d includes a hem punch 40 and an actuating mechanism 41 supporting the hem punch 40. The hem punch 40 is configured to be switchable between a pre-hemming position at which the associated bent portion of the sash is preliminarily hemmed and a standby position away from the bent portion of the sash by the actuating mechanism 41.

As shown in FIG. 2, on the bottom surface of the upper platen 2, a hem punch driver cam 50 for moving the hem punches 32 of the upper end hemming mechanism A is fixed above the slide cam 30. As shown in FIG. 5, the hem punch driver cam 50 is composed of a plate material extending downward. The lower half of the hem punch driver cam 50 has an engaging face 50 a engageable with the cam face 30 c of the slide cam 30. The engaging face 50 a is inclined along the cam face 30 c. The upper platen 2 constitutes a second platen of the hemming apparatus according to the present invention.

When the upper platen 2 is moved to its rising end, the hem punch driver cam 50 moves away from the slide cam 30. On the other hand, when the upper platen 2 is moved down, the hem punch driver cam 50 makes contact with the cam face 30 c of the slide cam 30 and engages it. Then, the slide cam 30 engaged with the hem punch driver cam 50 horizontally moves by being guided by a sliding plate (not shown) disposed on the lower platen 3. When the upper platen 2 is halfway through its downward movement, the hem punches 32 come to a pre-hemming position. When the upper platen 2 is further moved down to a position close to its descending end, the hem punches 32 come to a final hemming position. The upper platen 2 is configured to further move down a predetermined distance from the position at which the hem punches 32 come to their final hemming position.

The pre-hemming position is a position at which the pre-hemming part 32 c is pressed against the associated bent portion Wa of the workpiece W from laterally. The final hemming position is a position (shown in FIG. 8) at which the final hemming part 32 d faces the associated bent portion Wa from above. Therefore, the hem punch driver cam 50 is configured to change the hem punches 32 to their pre-hemming position and to their final hemming position. The amount and timing of horizontal movement of the hem punches 32 can be appropriately selected depending upon the shapes of the cam face 30 c and the engaging face 50 a.

As shown again in FIG. 2, also fixed on the bottom surface of the upper platen 2 are liners (load application mechanism) 53 for applying a downward processing load for final hemming to the hem punches 32. As shown in FIG. 5, each liner 53 is composed of a downwardly extending bar. The liners 53 are disposed so that its lower end surfaces can abut against the top surfaces of the hem punches 32 being in their final hemming position. On the other hand, when the hem punches 32 are in their pre-hemming position, the lower end surfaces of the liners 53 are set at vertical positions at which no downward processing load is applied to the hem punches 32. Furthermore, the liners 53 are configured to move down with downward movement of the upper platen 2 after switching of the hem punches 32 to their final hemming position and thereby apply a processing load to the hem punches 32 to move down the hem punches 32 against the urging forces of the springs 33 b. A downward load of the liners 53 may be applied to the hem punches 32 when the hem punches 32 are in their pre-hemming position.

Referring again to FIG. 2, on the bottom surface of the upper platen 2, driver cams 55 for moving the inner periphery hemming mechanisms B to D are provided to correspond to the positions of the inner periphery hemming mechanisms B to D. The amount and timing of movement of each of the upper end hemming mechanism A and the inner periphery hemming mechanisms B to D can be appropriately individually selected depending upon the shapes of the driver cam 50 for the upper end hemming mechanism A and the driver cams 55. Also provided on the bottom surface of the upper platen 2 are liners 58 for applying a processing load to the hem punches 42 of the inner periphery hemming mechanisms B to D.

Furthermore, driver cams 59 for moving the outer periphery pre-hemming mechanisms a, c and e and the outer peripheral corner pre-hemming mechanisms b and d are provided on the outer peripheral part of the bottom surface of the upper platen 2.

The upper platen 2 is further provided with an outer periphery final hemming punch 56 as disclosed, for example, in Japanese Patent Publication No. 3598489. Specifically, after the outer periphery pre-hemming mechanisms a, c and e and the outer peripheral corner pre-hemming mechanisms b and d preliminarily hem the outer periphery bent portions of the sash, the outer periphery final hemming punch 56 finally hems the outer periphery bent portions.

The upper platen 2 is further provided with pressers 57 for pressing the sash of the workpiece W against the hemming die 10. The pressers 57 are arranged along the shape of the sash.

Furthermore, as shown in FIG. 2, the upper platen 2 has a pad support mechanism 61 provided at a portion thereof corresponding to between the two hem punches 32 and 32 of the upper end hemming mechanism A. The pad support mechanism 61 supports the pad 60, which is to be pressed against the held portion Wb, to the upper platen 2. As shown in FIG. 9, the pad support mechanism 61 includes a base member 62 fastened to the bottom surface of the upper platen 2, a pad holding member 63 to which the pad 60 is attached, a plurality of parallel links 64 connecting the base member 62 to the pad holding member 63, and a tension spring 65 as a pad urging member urging the pad holding member 63 in a predetermined direction. The pad 60 extends beyond the pad holding member 63 towards the workpiece W. The bottom face of an extending distal end of the pad 60 is a workpiece holding face 60 a that is to bear against the held portion Wb.

The base member 62 is formed to extend long in an inner-to-outer direction of the upper platen 2. Parts of the parallel links 64 close to the base member 62 are supported to the base member 62 by substantially horizontally extending first shafts 71, while parts thereof close to the pad holding member 63 are supported to the pad holding member 63 by second shafts 72 extending in substantially parallel with the first shafts 71. Therefore, the pad holding member 63 can move in the inner-to-outer direction of the upper platen 2. The pad holding member 63 is provided with a cam follower 73 composed of a roller. The cam follower 73 is supported by a substantially horizontally extending pivot pin 74.

One end of the tension spring 65 is anchored to the parallel links 64, while the other end is anchored to a part of the base member 62 opposite to the workpiece W. The tension spring 65 urges the pad 60 in a direction to move the pad 60 away from the held portion Wb of the workpiece W (to the left in FIG. 9).

Furthermore, the lower platen 3 has, as shown in FIG. 1, a pad driver cam 77 provided at a portion thereof corresponding to the cam follower 73. The pad driver cam 77 is engageable with the cam follower 73. As shown again in FIG. 9, an upper part of the pad driver cam 77 has a cam face 77 a formed engageably with the cam follower 73. The cam face 77 a is inclined to become lower with approach to the hemming die 10. Thus, the pad driver cam 77 is configured to actuate the pad support mechanism 61 to switch the pad 60 between a position close to the held portion Wb of the workpiece W (the position shown in the solid lines in FIG. 9) and a position away from the held portion Wb (the position shown in the imaginary lines in FIG. 9). The shape of the cam face 77 a is set so that the workpiece holding face 60 a of the pad 60 bears against the held portion Wb of the workpiece W just before the hem punches 32 reach their pre-hemming position. The pad 60, the pad support mechanism 61 and the pad driver cam 77 constitute a workpiece holder 70.

Next, a description is given of hemming of the bent portions Wa and Wa of the workpiece W using the hemming apparatus 1 having the above structure. First, a workpiece W is put on the hemming die 10. Before this time, the body inner panel W1, the body outer panel W1, the reinforcing member W4, the sash inner panel, the sash outer panel and the channel member are joined together. Furthermore, the bent portions Wa and Wa of the workpiece W are previously press-formed to rise from the body. The workpiece W is put on the hemming die 10 so that the body outer panel W2 is located below the body inner panel W1 and bears on the hemming die 10. At the time when the workpiece W is put on the hemming die 10, the hem punches 32 and 40 are in their retracted positions away from the body inner panel W1 and the body outer panel W2 to avoid interference with the workpiece W.

Thereafter, when the upper platen 2 is moved down by the driving mechanism, the pressers 57 of the upper platen 2 first bear against the sash. Thus, the sash of the workpiece W is pressed from above against the hemming die 10 and set in place. Concurrently, the pad support mechanism 61 of the upper platen 2 moves down. Thus, the cam face 77 a of the pad driver cam 77 engages the cam follower 73 of the pad support mechanism 61, so that the pad 60 is changed to a position close to the held portion Wb of the workpiece W against the urging force of the tension spring 65. At the time, the upper platen 2 continues to move down. Thus, as shown in FIGS. 9, 10 and 11A, the pad 60 having reached the position close to the held portion Wb is pressed with its workpiece holding face 60 a against the held portion Wb of the workpiece W. The timing when the workpiece holding face 60 a is pressed against the held portion Wb is set at a point in time before the hem punches 32 apply hemming forces to the bent portions Wa and Wa.

Meanwhile, the downward movement of the upper platen 2 causes engagement of the engaging face 50 a of the hem punch driver cam 50 with the cam face 30 c of the slide cam 30 and then movement of the slide cam 30 towards the bent portions Wa of the workpiece W against the urging force of the spring 31 b of the slide cam urging mechanism 31. Thus, as shown in FIG. 6, the forming parts 32 b of the hem punches 32 enter between the body inner panel W1 and the body outer panel W2, the hem punches 32 reach their pre-hemming position, and the pre-hemming parts 32 c of the forming parts 32 b are pressed against their respective associated bent portions Wa. As a result, the bent portions Wa are folded and preliminarily hemmed. At the time, a processing load of the liners 53 has not yet been applied to the hem punches 32 and, therefore, the hem punches 32 are still floating-supported in their initial level. Just after the completion of the pre-hemming, the distal ends of the forming parts 32 b extend beyond the bent portions Wa of the workpiece W in the direction of their forward movement (to the right in FIG. 6) and the hem punches 32 reach their final hemming position. At the time, the workpiece W is still pressed by the pressers 57 of the upper platen 2 and the pad 60 and thereby restrained from displacement.

After the hem punches 32 are switched to their final hemming position, the liners 53 of the upper platen 2 apply a processing load to the hem punches 32. The hem punches 32 having received the processing load move down (in a processing direction) along the associated guide pins 36 against the urging forces of the associated springs 33 b. Thus, as shown in FIG. 7, the final hemming parts 32 d of the hem punches 32 are pressed against the bent portions Wa of the workpiece W, so that the bent portions Wa are finally hemmed into their final shapes. The state of the workpiece W at this time is shown in the enlarged view in FIG. 8.

The inner periphery bent portions and outer periphery bent portions of the sash are preliminarily hemmed and finally hemmed at the respective same timings of the preliminary hemming and final hemming of the bent portions Wa and Wa. As shown in FIGS. 3A and 3B, the timings of movements of the outer periphery pre-hemming mechanisms a, c and e and the outer peripheral corner pre-hemming mechanisms b and d are set so that the outer peripheral corner pre-hemming mechanisms b and d move earlier than the others. This setting of the timings of movements prevents interference of the outer periphery pre-hemming mechanisms a, c and e with the outer peripheral corner pre-hemming mechanisms b and d.

In this embodiment, as described previously, the hem punches 32 are floating-supported to the slide cam 30 of the lower platen 3 and the liners 53 of the upper platen 2 apply a processing load to the hem punches 32 being in their final hemming position. Therefore, without providing any cushion holder and any gas spring as in the known art, the hem punches 32 can be moved in the processing direction to finally hem the bent portions Wa of the workpiece W. Since the cushion holder and the gas spring are dispensed with, this simplifies the structure of the hemming apparatus and enhances the maintainability thereof. In addition, since a processing load is applied to the hem punches 32 for processing the bent portions Wa of the workpiece W, no strain is placed on the hemming apparatus 1, which elongates the lifetime of the hemming apparatus 1.

Furthermore, since the hem punches 32 are supported by the springs 33 b, the hem punches 32 can be floating-supported with a simple structure, thereby reducing the cost.

Furthermore, since the held portion Wb of the workpiece W between the bent portions Wa and Wa is held by the pad 60, this prevents displacement of the bent portions Wa and Wa located on both sides of the held portion Wb. Thus, the processing precision of the bent portions Wa and Wa of the workpiece W can be further increased.

Furthermore, in this embodiment, a plurality of driver cams 50 and 55 are provided, one for each of the upper end hemming mechanisms A and the inner periphery hemming mechanisms B to D. Therefore, when the bent portions Wa and sash inner periphery bent portions of the workpiece W have different shapes, the hem punches 32 and 40 can be moved independently of one another according to the shapes of these bent portions. Thus, the bent portions Wa and the inner periphery bent portions can be concurrently hemmed by applying hemming forces to all these bent portions at the same timing. Hence, the deformations of the bent portions Wa and the inner periphery bent portions can be reduced as compared to when these bent portions are hemmed at different timings.

Although in the above embodiment the hem punches 32 are floating-supported by the springs 33 b, the means for floating-supporting the hem punches 32 is not limited to the above springs. For example, the hem punches 32 may be floating-supported by gas springs or various types of elastic members.

Although in the above embodiment the pad 60 is supported by parallel links 64, the means for supporting the pad 60 is not limited to the parallel links and may be, for example, a single link or a slide rail.

The slide cam 30 may be urged by a gas spring instead of the spring 31 b.

The workpiece holder 70 may be dispensed with.

Although the above embodiment describes the case of hemming of a panel constituting part of a vehicle door using the hemming apparatus 1 according to the present invention, the hemming apparatus 1 can be used also when hemming various metallic panels other than vehicle door panels.

INDUSTRIAL APPLICABILITY

As can be seen from the above description, the hemming apparatus according to the present invention is suitable for hemming of, for example, a panel constituting part of a door for a motor vehicle. 

1. A hemming apparatus for hemming a bent portion of a workpiece previously formed to rise from the body of the workpiece, the hemming apparatus comprising: a first platen including a hemming die for supporting the workpiece, a hem punch including a pre-hemming part and a final hemming part both for hemming the bent portion of the workpiece, a slide cam to which the hem punch is attached, a slide cam guide mechanism for guiding the slide cam in a direction to laterally move the slide cam towards and away from the bent portion, and a hem punch support mechanism for floating-supporting the hem punch to the slide cam; and a second platen disposed to face the first platen and including a hem punch driver cam engageable with the slide cam and a load application mechanism for applying a processing load to the hem punch, the hem punch driver cam being configured to move the slide cam to change the hem punch to a pre-hemming position at which the pre-hemming part is pressed against the bent portion of the workpiece and to a final hemming position at which the final hemming part faces the bent portion of the workpiece, the load application mechanism being configured to apply a processing load to the hem punch being in the final hemming position.
 2. The hemming apparatus of claim 1, wherein the hem punch support mechanism includes a hem punch urging member urging the hem punch opposite to a direction in which the processing load is applied.
 3. The hemming apparatus of claim 1, wherein the hemming apparatus further includes a workpiece holder for holding a held portion formed in the workpiece by pressing the workpiece holder against the held portion, the workpiece holder includes a pad bearable against the held portion of the workpiece, a pad support mechanism for supporting the pad to the second platen and moving the pad in a direction towards and away from the held portion of the workpiece, and a pad driver cam disposed on the first platen and engageable with the pad support mechanism, and the pad driver cam is configured to actuate the pad support mechanism to switch the pad between a position close to the held portion of the workpiece and a position away from the held portion.
 4. The hemming apparatus of claim 3, wherein the pad support mechanism includes a link connecting the pad to the second platen, and a pad urging member urging the pad in a direction away from the held portion of the workpiece.
 5. The hemming apparatus of claim 3, wherein the hem punch comprises a plurality of spaced-apart hem punches, and the pad of the workpiece holder is disposed between each two adjacent said hem punches. 